Downgrade to OpenJDK 8

I had the same problem in Xubuntu 18.04 with Eclipse 2018-12 (4.10.0). It was working fine, but probably some update in the system (or to OpenJDK specifically) started this problem. In addition Gradle Tasks weren't showing up in the Gradle Window.

I solved the issue removing packages: default-jre, default-jdk, default-jre-headless, default-jdk-headless, all of them are "pointing at" openjdk-11.

Then I installed packages: openjdk-8-jre, openjdk-8-jdk, openjdk-8-jre-headless and openjdk-8-jdk-headless.

Change eclipse.ini's vm section to:-vm /usr/lib/jvm/java-8-openjdk-amd64/bin

And now everything is working fine, and Gradle tasks are showing again. To clarify, I'm also using LibGDX.

Switch libGDX from lwjgl to lwjgl3

I had the same issue as you with OpenJDK 11 / Java 11 (openjdk 11.0.10 2021-01-19). What fixed it was switching to lwjgl3 everywhere, which incidentally also fixed some other issues for me! (whole screen going black when I exit the app, mouse cursor capture only partially working, etc)

In build.gradle change the first into the second block:

api "com.badlogicgames.gdx:gdx-backend-lwjgl:$gdxVersion"

api "com.badlogicgames.gdx:gdx-backend-lwjgl3:$gdxVersion"

Also adjust your imports (e.g. in the DesktopLauncher class):

import com.badlogic.gdx.backends.lwjgl.LwjglApplication;import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;

import com.badlogic.gdx.backends.lwjgl3.Lwjgl3Application;import com.badlogic.gdx.backends.lwjgl3.Lwjgl3ApplicationConfiguration;

lwjgl3 should be almost entirely compatible, in my case I just needed to update the config:

LwjglApplicationConfiguration config = new LwjglApplicationConfiguration();config.samples = 8;config.height = 720;config.width = 1280;config.vSyncEnabled = true;new LwjglApplication(new RangeAnxietyGame(), config);

Lwjgl3ApplicationConfiguration config = new Lwjgl3ApplicationConfiguration();config.setBackBufferConfig(8, 8, 8, 8, 16, 0, 8);config.setWindowedMode(1280, 720);config.useVsync(true);new Lwjgl3Application(new RangeAnxietyGame(), config);

Replace openjdk-11 with adopt-openjdk-11

This problem also showed up for me while using libgdx on Ubuntu 20.04 with openjdk-11.

After a longer struggle I tried another JDK vendor instead of openjdk. This solved my issue. For some reason adopt-opendjk-11 works, while openjdk-11 was not working.